New security measures at US airports

I cannot help with the new measures because they were just put in, so there has been no time to really evaluate them. I would just keep abreast of the news - if there are major meltdowns in large US airports (especially during heavy travel period like Labor Day in the US in September), there will be plenty of press coverage.

It's about 45 minutes each way from O'Hare to the Chicago "Loop" downtown. Here is the info:
http://www.transitchicago.com/blueline/
I don't think a cab would be any faster and could get stuck in traffic, the blue line is fairly inexpensive and reliable.
Eight hours is really long, so I would probably try to see something, even though you won't get much time to do it. If you do get stuck at the airport, there are some delicious places to eat - I recommend Rick Bayless' Frontera Grill (you can Google the exact terminal info for location). ORD is an incredibly busy airport and most flights don't depart or arrive on time, so I would play by ear since your 8 hour window may turn out shorter or longer than that.

I know of no changes for Canadian nationals.

Make sure your air carrier has the trusted traveler ID so you can use the TSA Pre feature that comes with Nexus. Verify that your terminal has it.

I suspect you are going through OHare and not Midway. Take the Blue Line downtown. Allow a minimum of 1 hour transit time each way. Security lines at Chicago can get really long so you will need to account for that too.

That said, I believe you have enough time to see Michigan Ave or take a boat tour.

"I believe you have enough time to see Michigan Ave or take a boat tour. "

Michigan Avenue, yes. Boat tour - be careful. Some of the boats only go on the river, but some go both on the river and Lake Michigan. To go between the river and the lake, you have to go through locks. This takes a long time, and you could easily miss your plane. To me, the view of the city from the lake wasn't worth the extra time. The views from the river, on the other hand, are very interesting, particularly if you take an architecture tour.

Since it takes an hour each way from the airport to the center, and since you have to be back at ORD to go through security, I'd play it by ear. If your arriving flight is on time and if there are no unusual delays at security and if there is no disruption on the Blue line to the airport, you could do it. If any of these things are disrupted, don't chance it.

Check carefully where your flight to Brazil will depart from. All international flights that do not have preclearance arrive at Terminal 5, where the customs and immigration processing facilities are. But since you do not go through customs or passport control on departure from the US, international flights can depart from any terminal, and it can be different from the arrival terminal. Similarly, since your flight from Canada will have preclearance, it can arrive at any terminal.

It also depends on which airline you are taking from Chicago to Brazil. Not all airlines participate in Pre-Check.

Last week I was pulled out of the Pre-Check line when I was randomly selected to have all my electronics tested to make sure they were safe. That wasted 10 minutes. (By the way, this has nothing to do with what they saw. After walking through the metal detector with no problem, the alarm went off. They grabbed "my" bags, walked over to an inspection station and told me to stay behind the line. I had to tell them that those weren't my bags. We we went to get my actual bag and started the whole farce over again.)

No one really knows what the "new security" entails, as our government is no longer even remotely trying to be transparent. And we don't really know what things are going to be like in the months to come. As a safeguard, consider removing your social media apps from any devices you own, and making any accounts private so people can't find you by searching. It is a fact that some Canadians have been refused access to the US based on their political activity and/or ethnicity and/or religion.

Other than that, there's not much you can do. Sorry we're sort of in a meltdown over here. Please send help....

As for Chicago, do not try to take a cab. It will likely not be faster than the blue line. You should have time for nice walk around the Loop and Michigan Avenue.

I had an 8 hour layover in Chicago and I took the train downtown, spent an hour in the Art Institute seeing a few highlights, took a 1-1/2 hour boat ride (river only, concentrating on the architecture), walked around the loop a bit and checked out Navy Pier, and then took the train back to the airport 2 hours before my flight. If the weather is good I would recommend a boat or walking tour. I find that Chicago can be dismal in the rain and, if that's the case, you can do the Art Institute or the Aquarium. In your place I would go for it, 8 hours is too long to spend in an airport.

You have enough time to go down town for 3 hours

If you like architecture, Frank Lloyd Wright, etc. an alternative to going to the Loop would be to take a cab to Oak Park. You can check to see about hours and times for visiting his house and studio.

Traveling out of ORD all the time and some of these comments are good while others are not. No "locks" to get from the river to Lake Michigan. The river cruises are architectural tours, unless you go to navy pier for a sky line cruise (best in the evening). Plan on 2 hours to get to the "loop" from ORD and back. The flights tend to get in late and you never know how long it will take to get thru customs and recheck luggage, but they WILL leave on time and you will need to go thru security again. !

The Oak Park suggestion is very good. A cab to Oak Park should only take 30 min. (we lived there)

Seeing the Art Institute is worth whiled. After visiting major art museums in Europe, we were told that the Art Institute of Chicago was a major art museum of the world. Made me pretty proud to be a member.

There are bridges over the river in Chicago that do raise a few times a day, but the Chicago river architecture tour is a smaller boat that goes under the bridges' span.

If you want to go to the Art Institute (which I wholeheartedly recommend) might want to plan to make that your sole activity. It's a bit expensive to get in, and it's not a voluntary donation like the Met in NY.

If you are thinking of the Art Institute (one of the top art museums in the world), you will have to check any bags you have.